Air circuit breakers as described within U.S. Pat. Nos. 3,095,489 entitled "Manual Charging Means for Stored Energy Closing Mechanisms of Electric Circuit Breakers" and 3,084,238 entitled "Ratchet Mechanism for Charging a Closing Spring in an Electric Circuit Breaker" include operating mechanisms that are mainly exposed to the environment. Since the air circuit breakers are rated to carry several thousand amperes of current continuously, the exposure to convection cooling air assists in keeping the operating components within reasonable temperature limits.
U.S. patent application Ser. No. 08/878,598 entitled "Contact Position Indicator for an Industrial-Rated Circuit Breaker" describes the use of a target device to indicate the condition of the circuit breaker contacts as well as an interlock arrangement for preventing false indication thereof.
Various accessory devices are used with such air circuit breakers to provide auxiliary function along with overcurrent protection. One such accessory is the bell alarm accessory that provides local and remote indication as to the occurrence of circuit interruption. U.S. Pat. No. 5,502,286 entitled "Bell Alarm and Lock-Out for High Ampere-Rated Circuit Breakers" describes a bell alarm accessory used with so-called "insulated case" circuit breakers wherein the circuit breaker interrupting components are completely enclosed within an insulating plastic enclosure. This patent describes one such bell alarm accessory that interacts with the circuit breaker operating mechanism to activate the bell alarm upon circuit interruption and to prevent the closing of the circuit breaker contacts until the accessory is manually reset.
U.S. patent application Ser. No. 08/878,595 entitled "Circuit Breaker Bell Alarm Accessory with Lockout" provides a bell alarm accessory that provides local as well as remote indication of such circuit interruption as well as preventing circuit breaker contact closure until and unless the accessory has become manually reset.
In most circuit breakers employing a bell alarm for status indication of the circuit breaker contacts, it is a requirement that the circuit breaker operating mechanism be reset before the bell alarm can be manually reset to indicate the circuit breaker closed condition. It would be more convenient, in certain applications, to allow the bell alarm accessory to become automatically reset immediately upon closure of the circuit breaker contacts without the requirement of manual intervention.
U.S. patent application Ser. No. 08/904,324 entitled "Circuit Breaker Bell Alarm Accessory with Automatic Reset" filed on Jul. 31, 1997 describes a bell alarm accessory that is automatically reset upon response of the circuit breaker operating mechanism to close the circuit breaker contacts.
In certain industrial processes, the requirement with respect to the bell alarm accessory function may change in accordance with the process requirements. It would be advantageous to have a circuit breaker bell alarm accessory that can change function as well as to return to the early function without having to dismantle the circuit breaker operating mechanism enclosure to remove or to assemble separate bell alarm accessory units.
One purpose of the invention is to provide a multifunctional bell alarm unit that is capable of both automatic reset along with lock-out facility whereby either option can be adopted by a minor adjustment to a common bell alarm unit.